Universe Machine Corporation has for many years supplied power tongs into the Canadian and United States oil field market place. The power tongs have a throat for receiving an oilfield tubular. A ring gear driven by motors engages the oilfield tubular. A hydraulic system supplies hydraulic power fluid to motors that drive the ring gears. To prevent the oilfield tubular exiting the throat of the power tong during use, the throat has a gate or door. Cable or hydraulic mechanisms have been used to shut off the hydraulic supply to the motors when the gate or door is opened. Cable mechanisms sold recently by Universe Machine Corporation have used a two piece valve shut off that is difficult to adjust.